Far Harad is an entire continent of black folks who were historically victimized by the evil Numenoreans. It's a perfect plot for those who want to demonize white people and tell stories about Arda that are relevant to current socio-political issues. It's a lot better than the historical basis for The Woman King, that's for sure. Sauron was basically playing both sides against each other: convincing the Numenoreans to colonize Far Harad and perform human sacrifice, turn the Haradrim against the Numenoreans, convincing some Numenoreans to go native and help the Haradrim fight off the colonizers, convincing the Black Numenoreans and their Haradrim allies to serve Sauron the Liberator, converting to the same religion that they were sacrificed for but with them in charge this time... it's a perfect way to illustrate not just the modern trendy "white people evil!" but also to illustrate how the disenfranchised can be radicalized and engage in monstrous acts in the belief that the ends justify the means. Which is very relevant to modern politics... so naturally Amazon won't touch it at all.
Oh, and if you want black elves, hobbits and dwarves then you could probably invent ethnic groups of them native to Far Harad. It's not like Tolkien is around today to hear fan complaints and make adjustments to his own legendarium.